Embolic coil delivery system with spring wire release mechanism

ABSTRACT

A medical device for placing an embolic device at a predetermined site within a vessel of the body including a delivery catheter and a flexible pusher member slidably disposed within the lumen of the catheter. An embolic device is retained within the delivery catheter by a mechanical interlocking mechanism which includes an engagement member attached to the distal end of the pusher member and extends through a retaining ring at the proximal end of the embolic device. A detachment member extends through an aperture at the distal end of the engagement member thereby locking the embolic device onto the pusher member. A kicker member which takes the form of a generally U-shaped wire spring which extends from the distal end of the pusher member and is biased so as to lift the retaining ring off of the engagement member to ensure the release of the embolic device when the detachment member is withdrawn from the aperture of the engagement member.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This patent application is a continuation-in-part of U.S. patentapplication Ser. No. 11/301,865, filed on Dec. 12, 2005 now U.S. Pat.No. 7,367,987, entitled, “Stretch Resistant Embolic Coil Delivery SystemWith Mechanical Release Mechanism,” which is a continuation-in-part ofU.S. patent application Ser. No. 11/143,052, filed on Jun. 2, 2005 nowU.S. Pat. No. 7,371,251, entitled, “Stretch Resistant Embolic CoilDelivery System With Mechanical Release Mechanism.”

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to a medical device for placing a stretchresistant embolic device at a predetermined site within a vessel of thehuman body, and more particularly, relates to a catheter-baseddeployment system for delivering an embolic device. This device isparticularly suited to transport an embolic device, such as a stretchresistant embolic coil, through the tortious vasculature of the humanbrain to a selected site within the vessel or within an aneurysm.

2. Description of the Prior Art

For many years, flexible catheters have been used to place variousdevices within the vessels of the human body. Such devices includedilation balloons, radiopaque fluids, liquid medications, and varioustypes of occlusion devices such as balloons and embolic coils. Examplesof such catheter-based devices are disclosed in U.S. Pat. No. 5,108,407,entitled, “Method and Apparatus for Placement of an Embolic Coil” andU.S. Pat. No. 5,122,136, entitled, “Endovascular ElectrolyticallyDetachable Guidewire Tip For The Electroformation Of Thrombus InArteries, Veins, Aneurysms, Vascular Malformations And ArteriovenousFistulas.” These patents disclose catheter-based devices for deliveringembolic coils to preselected positions within vessels of the human bodyin order to treat aneurysms, or alternatively, to occlude blood vesselsat a particular location.

Coils which are placed in vessels may take the form of helically woundcoils, or alternatively, may take the form of randomly wound coils,coils wound within coils or other such coil configurations. Examples ofvarious coil configurations are disclosed in U.S. Pat. No. 5,334,210,entitled, “Vascular Occlusion Assembly” and U.S. Pat. No. 5,382,259entitled, “Vasoocclusion Coil with Attached Tubular Woven or BraidedFibrous Covering.” Embolic coils are generally formed of a radiopaquemetallic material, such as platinum, gold, tungsten, or alloys of thesemetals. Often, several coils are placed at a given location to occludethe flow of blood through the vessel, or aneurysm, by promoting thrombusformation at the particular site.

In the past, embolic coils have been placed within the distal end of acatheter. When the distal end of the catheter is properly positioned,the coil may then be pushed out of the end of the catheter with a pushermember to release the coil at the desired location. This procedure forplacement of an embolic coil is conducted under fluoroscopicvisualization such that the movement of the coil through the vasculatureof the body may be monitored and the coil placed at the desiredlocation.

Another procedure involves the use of glue or solder for attaching thecoil to a guidewire, which in turn, is placed within a flexible catheterfor positioning the coil within the vessel at a preselected position.Once the coil is in the desired position, the coil is held in positionby the catheter and the guidewire is pulled proximally to thereby causethe coil to become detached from the guidewire and released from thecatheter. Such a coil positioning system is disclosed in U.S. Pat. No.5,263,964 entitled, “Coaxial Traction Detachment Apparatus and Method.”

Still another coil positioning procedure is that of having a catheterwith a socket at the distal end of the catheter for retaining a ballwhich is, in turn, bonded to the proximal end of the coil. The ball,which is generally larger in diameter than the outside diameter of thecoil, is placed in the socket within the lumen at the distal end of thecatheter and the catheter is then moved into a vessel in order to placethe coil at a desired position. Once the position is reached, a pusherwire with a piston at the end thereof is pushed distally from theproximal end of the catheter to push the ball out of the socket in orderto release the coil at the desired position. Such a system is disclosedin U.S. Pat. No. 5,350,397, entitled, “Axially Detachable Embolic CoilAssembly.”

Another procedure for placing an embolic coil within a vessel is that ofusing a heat releasable adhesive bond for retaining the coil at thedistal end of the catheter. One such system uses laser energytransmitted through a fiber optic cable to apply heat to the adhesivebond in order to release the coil from the end of the catheter. Such aprocedure is disclosed in U.S. Pat. No. 5,108,407, entitled “Method andApparatus for Placement of an Embolic Coil.”

Yet another coil deployment system incorporates a catheter having alumen throughout the length of the catheter and a distal tip forretaining the coil for positioning the coil at a preselected site. Thedistal tip of the catheter is formed of a material which exhibits thecharacteristic that when the lumen of the catheter is pressurized thedistal tip expands radially to release the coil at the preselected site.Such a deployment system is disclosed in U.S. Pat. No. 6,113,622,entitled, “Embolic Coil Hydraulic Deployment System.”

Still another coil deployment system incorporates an interlockingmechanism on the coil. The interlocking end on the embolic coil coupleswith a similar interlocking mechanism on a pusher assembly. A controlwire which extends through the locking mechanism secures the coil to thepusher assembly. The pusher assembly and embolic coil are initiallydisposed within the lumen of a catheter. When the embolic coil is pushedout of the end of the catheter for placement, the control wire isretracted and the coil disengages from the pusher assembly. Such adeployment system is disclosed in U.S. Pat. No. 5,925,059, entitled,“Detachable Embolic Coil Assembly.”

Yet another coil deployment system incorporates an embolic devicedetachably mounted on the distal portion of a pusher member and held inplace with a connector thread or fiber. The fiber passes through acutter member that may be activated to cut the connector fiber. Once theconnector fiber is cut, the embolic device is released. Such adeployment system is disclosed in Published U.S. Patent Application No.2002/0165569, entitled, “Intravascular Device Deployment MechanismIncorporating Mechanical Detachment.”

Still another coil deployment system incorporates an embolic device witha stretch resistant member therethrough. The distal end of the stretchresistant member attaches to the embolic coil and the proximal end ofthe stretch resistant member is detachably mounted on the pusher memberthrough various means such as adhesive, or by a connector fiber adheredto or tied to the pusher member, and is detachable by the application ofheat. Such a deployment system is disclosed in Published U.S. PatentApplication No. 2004/0034363, entitled, “Stretch Resistant TherapeuticDevice.”

Still another coil deployment system incorporates a pusher wire with astiff wavy-shaped end segment which is coupled to the embolic coil andis placed in the lumen of the catheter. The coil is advanced through thecatheter until it reaches a predetermined site in the vessel at whichtime the pusher wire is retracted and the embolic coil is released. Sucha system is disclosed in U.S. Pat. No. 6,203,547, entitled,“Vaso-occlusion Apparatus Having A Manipulable Mechanical DetachmentJoint And A Method For Using The Apparatus.”

A still further embolic device deployment system for placement of anembolic device, or coil, includes a delivery catheter and a flexiblepusher member. The embolic device is retained by an interlockingmechanism which includes a detachment member which extends through anaperture in an engagement member. The engagement member engages a ringon the embolic device. When the detachment member is withdrawn from theaperture, the embolic device is released. One such deployment system isdisclosed in a concurrently filed patent application U.S. Ser. No.11/143,051 entitled, “Embolic Coil Delivery System With MechanicalRelease Mechanism,” and assigned to the same assignee as the presentapplication.

SUMMARY OF THE INVENTION

The present invention is directed toward a vascular occlusive embolicdevice deployment system for use in placing an embolic device at apredetermined site within a vessel which includes an elongated flexiblecatheter, an elongated pusher member having a lumen extendingtherethrough and being slidably disposed within the lumen of thecatheter. The embolic device takes the form of an embolic coil defininga central lumen extending between the proximal and distal ends of thecoil and having a retaining ring disposed on the proximal end of thecoil. An engagement member is fixedly attached to the distal end of thepusher member and includes an aperture extending through the distal endthereof. The engagement member extends through the retaining ring of thestretch-resistant embolic device. The deployment system includes akicker member which takes the form of a generally U-shaped flexible wirespring extending from the distal end of the pusher member and having afirst leg embedded into a side wall of the pusher member and a secondleg embedded into an opposite side wall of the pusher member. The firstleg of said kicker member contacts the retaining ring of the embolicdevice and the first leg is normally biased to deflect in a directionwhich will cause the retaining ring of the embolic device to be liftedoff of the engagement member. In addition, the deployment systemincludes an elongated detachment member which extends from the proximalend of the pusher member, through the lumen of the pusher member andthrough the aperture of the engagement member such that when thedetachment member is pulled proximally the distal end of the detachmentmember is withdrawn from the aperture of the engagement member tothereby release the embolic device.

In accordance with another aspect of the present invention, the embolicdevice takes the form of an embolic coil for occluding an aneurysm.

In accordance with another aspect of the present invention, theengagement member is of a generally L-shaped configuration and one ofits legs is attached to the pusher member and the other leg extendsthrough the retaining ring. The aperture of the engagement memberextends through the leg which extends through the retaining ring suchthat when the detachment member extends through the retaining ring ofthe embolic device such that the embolic device is interlocked onto theengagement member until the detachment member is withdrawn from theaperture.

In accordance with another aspect of the present invention, the apertureof the engagement member has a central axis which extends generally at aright angle to the central axis of the retaining ring. In addition, theembolic device takes the form of a helically wound embolic coil having acentral axis which extends at a right angle to the central axis of theretaining ring.

In addition, the embolic device deployment system preferably includes aretaining clamp mounted on the proximal end of the pusher member, andthe detachment member extends from a position proximal of the retainingclamp and through a lumen in the clamp in order that the detachmentmember may be clamped in a fixed position prior to the release of theembolic device. Upon release of the clamp, the detachment member may bewithdrawn from the aperture of the engagement member to thereby releasethe embolic device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged, partially sectional view of an embodiment of anembolic device deployment system in accordance with the presentinvention;

FIG. 1A is an enlarged, partially sectional view of a second embodimentof an embolic device deployment system in accordance with the presentinvention;

FIGS. 2A through 2D are enlarged, sectional views, illustrating in moredetail the coil deployment system of FIG. 1A;

FIGS. 3 through 3C are enlarged, sectional views of the coil deploymentsystem shown in FIG. 1A illustrating the sequential steps in theadvancement of the embolic device, removal of a detachment member, andrelease of the embolic device.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 generally illustrates one embodiment of a vascular occlusiveembolic device deployment system 10 which includes a sheath introducer12 having a lumen 14 extending therethrough and having an elongatedpusher member 16 slidably disposed within the lumen 14 of the sheathintroducer 12. An elongated engagement member 18 extends distally fromthe pusher member 16 and has an aperture (to be described hereinafter)extending through the distal end thereof. The engagement member 18 ispreferably formed from a distal section of the wall and of the pushermember 16 but may be formed as a separate member attached to the distalend of the pusher member 16.

The deployment system 10 also includes an embolic device 23, which asillustrated, preferably takes the form of a helically wound emboliccoil, which is disposed in the distal section of the sheath introducer12. While the embolic device as illustrated is shown as a helicallywound coil various other types of embolic devices, such as filaments,braids, foams, expandable meshes and stents, could be delivered usingthe present deployment system and various other coil configurationscould be delivered using this system. A weld, or solder, bead 24 isformed at the distal end of the embolic device 23 to provide anatraumatic tip for the embolic device. In addition, the distal end of astretch-resistant member 25, which preferably takes the form of aplatinum wire, is attached to the distal bead 24 and extends proximallythrough the central lumen of the coil. While the stretch-resistantmember preferably takes the form of a platinum wire, other materials orcomposites such as polymers, metals and ceramics, having a lowelongation relative to the coil elongation may also be suitable.Alternatively, the distal end of the stretch-resistant member could beattached to the coil at a more proximal location in the distal sectionof the coil. A headpiece 21 which takes the form of a cylindrical memberis disposed on the proximal end of the embolic device 23. The headpiece21 includes a retaining ring 28 which extends proximally from thecylindrical shaped headpiece. The proximal end of the stretch resistantmember is then attached to the distal edge of the headpiece 21.Preferably, the retaining ring 28 has a central axis which extends atright angles to the central axis of the sheath introducer 12 and alsoextends at right angles to the central axis of the helically woundembolic coil.

FIG. 1A illustrates another variation of the stretch-resistant embolicdevice 23 in which the distal end of a stretch-resistant member 27 isattached to the bead 24 at the distal end of the coil and the proximalend of the stretch-resistant member is attached to the turns in theproximal section of the coil by use of a weld, or solder, bead 29.

As illustrated in FIGS. 1, 1A, 2A and 2B, the engagement member 18 is ofa generally L-shaped configuration and extends through the retainingring 28. An elongated detachment member 30 extends from the proximal endof the deployment system 10 and through a lumen in the pusher member 16and then through the aperture 22 (FIG. 2A) of the engagement member 18and serves the function of interlocking the embolic device 23 to thepusher member 16 until such time as the detachment member 30 iswithdrawn proximally. In order to improve the release mechanism anelongated kicker member 17 extends distally from the pusher member 16and preferably takes the form of a generally U-shaped flexible wirespring having both legs attached to the pusher member to form anaperture 19. As will be described in more detail, the upper leg of thekicker member 17 is normally biased in a direction which tends to liftthe retaining ring 28 off of the engagement member 18, but is preventedfrom doing so unless the elongated detachment rod 30 is withdrawn fromthe aperture 22 of the engagement member 18.

The detachment member 30 preferably takes the form of a small diameterelongate filament, however, other forms such as wires or tubularstructures are also suitable. While the detachment member 30 ispreferably formed of nitinol, other metals and materials such as,stainless steel, PTFE, nylon, ceramic or glass fiber and composites mayalso be suitable.

A Tuohy-Borst type of clamp 32 is mounted on the proximal end of thepusher member 16 and when tightened onto the detachment member 30 servesto prevent movement of the detachment member until such time as theclamping cap 34 is loosened to release the grip onto this member.

FIGS. 2A and 2B illustrate the interlocking arrangement between theembolic device 23 and the pusher member 16. More particularly, thesefigures illustrate the operation of the deployment system as the pushermember 16 is moved distally to a position so that the distal end of thepusher member 16 extends slightly out of the distal end of the sheathintroducer 12, or a delivery catheter, thereby releasing the embolicdevice 23.

As illustrated in FIGS. 2C and 2D, once the embolic device 23 has beenmoved out of the end of the sheath introducer 12, the detachment member30 may be pulled proximally to withdraw the detachment member from theaperture 22 of the engagement member 18 to thereby cause the engagementmember to disengage from the retaining ring 28 of the embolic devicethereby releasing the embolic device 23 at a preselected position. Thekicker member 17 which takes the form of a generally U-shaped flexiblewire spring which serves to ensure the release of the embolic device 23by applying a lifting force on the retaining ring 28 to lift theretaining ring from the engagement member 18. More particularly, theU-shaped spring wire kicker member 17 is attached to and extends fromthe distal end of the pusher member 16. One of the legs 17 a of thekicker member 17 is embedded into the wall of the tube which forms thepusher member 16 and the other leg 17 b of the kicker member 17 isembedded into an opposite wall of the pusher member to thereby form theU-shaped configuration of the kicker member. As illustrated in FIGS. 2Aand 2C, when the embolic device 23 is interlocked onto the distal end ofthe pusher member 16 for transport through the sheath introducer 12, theupper leg 17 a of the kicker member is deflected downwardly so as toapply a lifting force onto the retaining ring 28. The detachment member30 locks the retaining ring in place so that it may not be lifted untilsuch time as the detachment member 30 is withdrawn. Upon withdrawal ofthe detachment member 30, the kicker member lifts the retaining ring 28off of the engagement member 18 thereby releasing the embolic device 23.Alternatively, if desired, the detachment sequence described above andillustrated in FIGS. 2A through 2D may be executed while the embolicdevice 23 is still within the lumen of sheath introducer 12, or adelivery catheter.

One of the important advantages of the present invention is that theembolic device may be placed at a desired location within a vessel, orwithin an aneurysm, with the configuration of the device deploymentsystem as shown in FIGS. 2A and 2B. If it is determined that the embolicdevice is improperly positioned, the embolic device 23 may then bewithdrawn from that location and placed at another location, or evenremoved from the body by first withdrawing the pusher member 16 and theembolic device totally back into the delivery catheter. Once the embolicdevice has been entirely withdrawn back into the delivery catheter, thecatheter may then be moved to a more desirable location and the embolicdevice may then be released at the new location. With the addition ofthe stretch resistant member 27, the embolic device may be withdrawnwithout concern that the coil will stretch and become very difficult toremove.

FIGS. 3, 3A and 3B generally illustrate the sequence of placing anembolic device, such as a helical wound coil into an aneurysm 36 whichextends from a vessel wall 38. More particularly, FIG. 3 illustrates thevascular occlusive embolic device deployment system 10 in the sameconfiguration as shown in FIG. 1A after the pusher member and associatedembolic device have been inserted into a delivery catheter 35 andadvanced into a position for deployment of the embolic device 23, shownas a helical embolic coil, into the aneurysm 36. FIG. 3A illustrates thedeployment device having a configuration similar to FIG. 2A with theembolic device 23 being placed within the aneurysm 36 but prior towithdrawal of the detachment member 30. At this point, prior to thewithdrawal of the detachment member 30, as previously mentioned, if itis determined that the embolic device has been improperly placed, thepusher member may be withdrawn thereby withdrawing the embolic deviceback into the delivery catheter 35 for repositioning to a differentlocation, or alternatively, to remove the embolic coil entirely from thebody.

FIG. 3B illustrates the deployment device after the detachment member 30has been removed from the engagement member 18 thereby releasing theembolic device within the aneurysm 36, and FIG. 3C illustrates thedeployment device after the pusher member 16 has been withdrawn backinto the delivery catheter 35 at the completion of the procedure oralternatively in order to insert a second coil through the deliverycatheter 35 and into the same aneurysm.

As is apparent, there are numerous modifications of the preferredembodiment described above which will be readily apparent to one skilledin the art, such as many variations and modifications of the embolicdevice including numerous coil winding configurations, or alternativelyother types of embolic devices. Also, there are many possible variationsin the materials and configurations of the release mechanism. Thesemodifications would be apparent to those having ordinary skill in theart to which this invention relates and are intended to be within thescope of the claims which follow.

1. A vasooclusive embolic device deployment system for use in placing anembolic device at a predetermined site within a vessel comprising: anelongated flexible deployment catheter having a lumen extendingtherethrough and having proximal and distal ends; an elongated tubularpusher member having a lumen extending therethrough and having proximaland distal ends and being slidably disposed within the lumen of thedeployment catheter; an embolic device having a proximal end, aretaining ring being disposed at the proximal end thereof; an engagementmember extending from the distal end of the pusher member and having anaperture extending through the distal end thereof, said engagementmember extending through said retaining ring; a kicker member whichtakes the form of a generally U-shaped wire spring having first andsecond legs extending from the distal end of the pusher member andhaving the end of said first leg attached to a side wall of the pushermember and the end of said second leg attached to an opposite side wallof the pusher member, said first leg of said kicker member contactingsaid retaining ring of said embolic device and being normally biased todeflect in a direction which causes said retaining ring to be lifted offof said engagement member; and, an elongated detachment member extendingfrom a position proximal of the proximal end of the pusher member,through the lumen of the pusher member and through the aperture of theengagement member such that when the detachment member is pulledproximally the distal end of the detachment member is withdrawn from theaperture of the engagement member and said kicker member lifts saidretaining ring of said embolic device off of said engagement member tothereby release the embolic device from said pusher member.
 2. Avasooclusive embolic device deployment system as defined in claim 1,wherein said first leg of said U-shaped kicker member is embedded intothe wall of the pusher member and said second leg of said U-shapedkicker member is embedded into an opposite side wall of said pushermember.
 3. A vasooclusive embolic device deployment system as defined inclaim 1, wherein said engagement member is of a generally L-shapedconfiguration so as to form first and second legs, said first leg beingattached to said pusher member and said second leg extending throughsaid retaining ring.
 4. A vasooclusive embolic device deployment systemas defined in claim 3, wherein said aperture of said engagement memberextends through the distal end of said second leg of said engagementmember such that when said detachment member extends through saidaperture said retaining ring of said embolic device is interlocked ontosaid engagement member until the detachment member is withdrawn fromsaid aperture.
 5. A vasooclusive embolic device deployment system asdefined in claim 1, wherein said embolic device takes the form of anembolic coil comprised of multiple turns.
 6. A vasooclusive embolicdevice deployment system as defined in claim 5 wherein said embolicdevice takes the form of a helically wound embolic coil.
 7. Avasooclusive embolic device deployment system as defined in claim 6,wherein a central axis of said retaining ring extends substantially at aright angle to a central axis of said helically wound embolic coil.
 8. Avasooclusive embolic device deployment system as defined in claim 6,wherein said helically wound embolic coil is comprised of a plurality ofturns of which one of said plurality of turns has a central axis whichextends substantially at a right angle to a central axis of the otherturns and forms the retaining ring.
 9. A vasooclusive embolic devicedeployment system as defined in claim 1, including a retaining clamphaving a lumen extending therethrough and being mounted on the proximalend of the pusher member, and wherein said detachment member extendsfrom a position proximal of said clamp and through the lumen of theclamp so that said detachment member may be clamped into a fixedposition prior to the release of the clamp and withdrawal of thedetachment member from the aperture of the engagement 20 member.
 10. Avasooclusive embolic device deployment system for use in placing anembolic device at a predetermined site within a vessel comprising: anelongated flexible deployment catheter having a lumen extendingtherethrough and having proximal and distal ends; an elongated pushermember having a lumen extending therethrough and having proximal anddistal ends and being slidably disposed within the lumen of thedeployment catheter; an embolic device having a proximal end, aretaining ring being disposed at the proximal end thereof; an engagementmember extending from the distal end of the pusher member and having anaperture extending through the distal end thereof, said engagementmember extending through said retaining ring; a kicker member whichtakes the form of a generally U-shaped wire spring having first andsecond legs extending from the distal end of the pusher member andhaving the end of said first leg attached to one side of the distal endof the pusher member and the end of said second leg attached to anopposite side of the distal end of the pusher member, said first leg ofsaid kicker member contacting said retaining ring of said embolic deviceand being normally biased to deflect in a direction which causes saidretaining ring to be lifted off of said engagement member; and, anelongated detachment member extending from a position proximal of theproximal end of the pusher member, through the lumen of the pushermember and through the aperture of the engagement member such that whenthe detachment member is pulled proximally the distal end of thedetachment member is withdrawn from the aperture of the engagementmember and said kicker member lifts said retaining ring of said embolicdevice off of said engagement member to thereby release the embolicdevice from said pusher member.
 11. A vasooclusive embolic devicedeployment system as defined in claim 9, wherein said first and secondlegs of said U-shaped kicker member are embedded into said pushermember.
 12. A vasooclusive embolic device deployment system as definedin claim 10, wherein said engagement member is of a generally L-shapedconfiguration so as to form first and second legs, said first leg beingattached to said pusher member and said second leg extending throughsaid retaining ring.
 13. A vasooclusive embolic device deployment systemas defined in claim 12, wherein said aperture of said engagement memberextends through the distal end of said second leg of said engagementmember such that when said detachment member extends through theaperture of said retaining ring of said embolic device is interlockedonto said engagement member until the detachment member is withdrawnfrom said aperture.
 14. A vasooclusive embolic device deployment systemas defined in claim 10, wherein said embolic device takes the form of anembolic coil comprised of multiple turns.
 15. A vasooclusive embolicdevice deployment system as defined in claim 14, wherein said embolicdevice takes the form of a helically wound embolic coil.
 16. Avasooclusive embolic device deployment system as defined in claim 13,wherein a central axis of said retaining ring extends substantially at aright angle to a central axis of said helically wound embolic coil. 17.A vasooclusive embolic device deployment system as defined in claim 16,wherein said helically wound embolic coil is comprised of a plurality ofturns of which one of said plurality of turns has a central axis whichextends substantially at a right angle to a central axis of the otherturns and forms the retaining ring.